QUANTITATION OF MATERNAL-FETAL IGG TRANSPORT IN THE CHICKEN

  • 1 January 1985
    • journal article
    • research article
    • Vol. 54  (4) , 755-762
Abstract
Quantitative and temporal features of maternal-fetal transport of IgG in the chicken were determined by means of a sensitive and specific radioimmunoassay. The 1st step in this 2-step process is the transport of maternal IgG from the hen plasma across the oolemma into the maturing oocyte in the ovarian follicle. Oocytes sequester IgG throughout most of their maturation from 10 mg pre-vitellogenic oocytes to fully mature 20 g oocytes ready to be shed into the oviduct. IgG uptake is exactly proportional to mass accumulation at every point. Thus, the concentration of IgG in the yolk is invariant throughout maturation of the oocyte (.apprx. 8 mg/ml) and the rate of uptake in this single specialized cell can be as great as 45 mg/day during its last 3 days of growth before ovulation. The 2nd step, uptake of yolk IgG across the yolk sac and into the fetal circulation, is detectable at the earliest time points tested (day 7), but accumulation into the embryonic plasma occurs at a relatively low rate (< 100 .mu.g/day) until a dramatic increase in uptake (> 600 .mu.g/day) occurs in the last 3 days before hatching. The hatchling has 1-2 mg/ml of maternal IgG in its plasma. Increase in IgG uptake lags significantly (.apprx. 4 days) behind increase in mass by the developing embryo, suggesting that IgG uptake occurs predominantly in the last few days before hatching. This ensures that the hatching is endowed with those maternal IgG which will be its planopy when in enters the hostile world.